The present invention relates to photographic cameras, having a system for exposure metering through the objective, with selective switching between an integrated and a selected measurement.
Such a camera, the disclosure of which is incorporated herein, is disclosed in the U.S. Pat. Nos. 3,532,043 and 3,884,584.
It is known from these prior art cameras to provide two photoresistors behind the picture taking lens, one of which is used for an integrated measurement and the other for a selected measurement. It is known to switch from one to the other of these integrated and selective measurements. However, the design also may be such that only one photoresistor is used for the selective measurement, while a second photoresistor is added for the integrated measurement, so that for the integrated one, both are used.
In any event, switching from one measurement to the other requires some electrical switching, reversal or hooking up. However direct electrical switching is impossible when modern photoelectric transducers in the form of silicon-, or gallium-arsenide-phosphorus-diodes are used in lieu of the prior photoresistors. Commercial examples of these diodes are, for example, the type VTB 9416 B of Messrs. VACTEC, Inc., 2423 Northline Ind. Blvd., Maryland Heights, Mo. 63043, USA and type BS 2030 B of Messrs. SHARP, Japan. This is due to the extremely minute currents passing through these diodes. Amplifiers are required in order to switch these diodes, but these amplifier systems and the associated switches are complex and costly.